- ID:
- ivo://CDS.VizieR/J/ApJ/872/16
- Title:
- Integrated star formation law revisited. I.
- Short Name:
- J/ApJ/872/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use new and updated gas- and dust-corrected star formation rate (SFR) surface densities to revisit the integrated star formation law for local "quiescent" spiral, dwarf, and low surface brightness galaxies. Using UV-based SFRs with individual IR-based dust corrections, we find that "normal" spiral galaxies alone define a tight Σ<SUB>(HI+H2)–Σ</SUB>SFR_ relation described by an n=1.41<SUB>–0.07</SUB><SUP>+0.07</SUP> power law with a dispersion of 0.28<SUB>–0.02</SUB><SUP>+0.02</SUP> (errors reflect fitting and statistical uncertainties). The SFR surface densities are only weakly correlated with HI surface densities alone, exhibiting a stronger and roughly linear correlation with H<SUB>2</SUB> surface densities, similar to what is seen in spatially resolved measurements of disks. However, many dwarf galaxies lie below the star formation law defined by spirals, suggesting a low-density threshold in the integrated star formation law. We consider alternative scaling laws that better describe both spirals and dwarfs. Our improved measurement precision also allows us to determine that much of the scatter in the star formation law is intrinsic, and we search for correlations between this intrinsic scatter and secondary physical parameters. We find that dwarf galaxies exhibit second-order correlations with the total gas fraction, stellar mass surface density, and dynamical time, which may explain much of the scatter in the star formation law. Finally, we discuss various systematic uncertainties that should be kept in mind when interpreting any study of the star formation law, particularly the X(CO) conversion factor and the diameter chosen to define the star-forming disk in a galaxy.
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- ID:
- ivo://CDS.VizieR/J/ApJ/702/506
- Title:
- The Clowes-Campusano LQG Survey. I.
- Short Name:
- J/ApJ/702/506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of galaxy structures on large scales is a key observational prediction for current models of galaxy formation. The Sloan Digital Sky Survey (SDSS) and the 2dF galaxy survey have revealed a number of structures on 40-150h<SUP>–1</SUP>Mpc scales at low redshifts, and some even larger ones. To constrain galaxy number densities, luminosities, and stellar populations in large structures at higher redshift, we have investigated two sheet-like structures of galaxies at z=0.8 and 1.3 spanning 150h<SUP>–1</SUP> comoving Mpc embedded in large quasar groups (LQGs) extending over at least 200h<SUP>–1</SUP>Mpc. We present first results of an analysis of these sheet-like structures using two contiguous 1° Galaxy Evolution Explorer (GALEX) fields (FUV and NUV) cross-correlated with optical data from the SDSS. We derive a sample of 462 Lyman break galaxy (LBG) candidates coincident with the sheets. Using the GALEX and SDSS data, we show that the overall average spectral energy distribution of a LBG galaxy at z∼1 is flat (in f<SUB>λ</SUB>) in the rest-frame wavelength range from 1500Å to 4000Å, implying evolved populations of stars in the LBGs. From the luminosity functions we get indications for overdensities in the two LQGs compared to their foreground regions.
